Mars in short: past and present geology and climate

Mars is the fourth planet from the Sun. Today it is cold, dry, and covered by a reddish bedrock and regolith. The surface is little protected from radiation due to a thin atmosphere and the lack of a substantial magnetic field. It is however thought to have been very different: that in its early history, about 4 Gyr ago, it had a thicker atmosphere and a magnetic field. Water seems to have flown, at least periodically, on the surface. It might even have harboured life. In this chapter, the major developments in Mars’s geological history, as well as its current environmental conditions, are laid out. They are then discussed in the context of space exploration. Our analysis suggests that resources for human explorers may be sourced on site, notably water, building materials, and nutrients for growing food. It also highlights the many hazards which would be faced on Mars, including radiation, a toxic and oxidizing soil, little organic material, and a harsh climate.